The present invention is generally directed to the detection and retrospective analysis of the critical events associated with non-compliant or dangerous operations carried out by operators of cranes. More particularly, the present invention is directed to a system and method for automatically collecting, processing and storing data representative of crane operating conditions causing such non-compliant or dangerous operations, for later retrieval and analysis.
Lifting and positioning of heavy objects is one of the basic tasks in construction. A wide variety of types of cranes, derricks and other hoisting equipment, both mobile and permanently installed, are used to carry out specific lifting and positioning operations. In the past, safe crane operations depended on operator training, good maintenance, effective planning, and supervision. Safety is considered to be among the most critical issues involved in the success of any lift operation. However, crane accidents still occur. Such accidents often involve serious personal injury or death and costly destruction of property, as well as costly damage to the crane itself such as crane boom bending and turret drive gear failure.
Studies have shown that crane operators often expose cranes to frequent uncharacteristic loading conditions, such as the dragging of waste buckets and the extrication or extraction of piles, tree stumps and lodged debris. The culpability of crane operators is often attributed to lack of sufficient information regarding crane capacities, poor planning or miscalculations regarding anticipated load conditions, poor decision-making during crane operation, and simply carelessness. Dragging and extrication events constitute overload conditions and can cause several types of failure modes and resulting damage, such as the creation of grooves on sheave pulleys, plastic deformation and even complete failure of the boom, and breakage of gear teeth in the turret drive. Grooving and gear teeth breakage are directly related to hoist cable load vectors with significant components off the normal axis and are induced during the dragging of loads. Boom deformation and failure can result from overloading the boom by exceeding safe loading capacities for the different boom angles and boom extensions specified by capacity charts provided by crane manufacturers. Deformation can also result from the cumulative effect of static and dynamic forces that occur during the abrupt extrication events.
In order to assist the crane operator and secure the crane from damages, overload protection systems based on hydraulic pressure limits are provided as standard in many new cranes. These overload protection systems, however, do not secure the crane against dragging or extrication events. In addition, operators often choose to ignore the warning signals from the protection system and consequently operate cranes at dangerous hydraulic pressure levels.
Presently, no adequate means exist for detecting the occurrence of hazardous dragging and extrication events or for recording such events. Accordingly, a need exists for a crane monitoring system capable of detecting such events, providing an audible warning to the crane operator of detected event, and automatically storing electronic data descriptive of the actual event for later analysis by skilled investigators.
The crane monitoring system and method according the present invention can generally be characterized by a plurality of sensors mounted to a crane which communicate data to an on-board control unit. The control unit is characterized by having xe2x80x9cblack boxxe2x80x9d functionality. In general, the control unit processes and stores input data which will indicate either normal or unsafe crane conditions. Unsafe crane conditions are defined as alarm events such as dragging and extrication events. Each stored event has a time and date stamp indicating the time at which the event occurred and the time when the event is cleared. The control unit stores the latest event in a record format until the device memory is filled. The control unit rolls over the data after the memory is filled, erasing the oldest record in order to store the most recent record.
The input data from sensors is digitized and stored continuously. The processing circuitry of the control unit compares the input data to a predetermined set of parameters to detect whether an alarm event has occurred. Upon detection of an alarm condition, a horn output is activated. The control unit then logs data from the sensors into a non-volatile memory, along with the data from a period of time such as ten seconds prior to the alarm. Data is stored continuously until the alarm event clears and then, for a period of time such as thirty seconds, additional data is stored after the conclusion of the alarm event. This results in a discrete event log residing on the non-volatile memory which can subsequently be accessed by authorized personnel for analysis and identification of the crane operator who caused the alarm event. The event log can be downloaded to a PC in comma delimited format so that it can be used by any common spreadsheet program.
According to one embodiment of the present invention, a method is provided for monitoring critical operations of a crane, and for safely and automatically storing records of alarm events arising from such operations the method comprises the following steps. A plurality of input channels are provided, over which crane condition signals can be transferred from sensors mounted to a crane. Each crane condition signal is generated by one of the sensors, and includes a value representative of a specific measurement or condition of the crane during operation thereof. A data set is continuously sampled at a predetermined sampling rate during operation of the crane by communicating with the input channels. Each sampled data set includes the value detected for each crane condition signal at the time of sampling, and also includes time and date information corresponding to the respective time and date of sampling. Given the significant transfer speed of electrical signals and the processing speed of modem digital processing devices, the time of sampling substantially corresponds to the time at which the crane condition occurred.
Each data set sampled is stored into a non-volatile memory device. For each data set sampled, the values of the crane condition signals are compared to a set of predetermined safe operating parameters to determine whether an alarm event has occurred. The alarm event is defined when one or more of the values of the sampled crane condition signals falls outside a corresponding one or more of the safe operating parameters. If an alarm event has occurred, the values of the crane condition signals are compared to the safe operating parameters to determine whether the alarm event has ceased. The cessation of the alarm event is defined when one or more of the values of the sampled crane condition signals falls back inside a corresponding one or more of the safe operating parameters. If an alarm event has occurred, an event log is generated for the alarm event by storing, into a separately addressed location of the non-volatile memory device, all data sets sampled over a period of event history. The period of event history is defined as starting at a predetermined number of seconds prior to the occurrence of the alarm event and ending at a predetermined number of seconds after the cessation of the alarm event.
According to another embodiment of the present invention, the method of crane monitoring includes mounting the plurality of sensors to a crane, and securely mounting a control unit to the crane. Control circuitry is provided within the control unit. The plurality of input channels are provided to establish communication from the sensors to the control circuitry. The control circuitry is programmed to perform the crane monitoring and data storage functions described hereinabove, including sampling the data set, storing the data set into the non-volatile memory, detecting the occurrence of an alarm event, and generating an event log by storing all data sets sampled over the period of event history.
According to a further aspect of the present invention, a crane monitoring system is provided. The crane monitoring system comprises a plurality of sensors as described hereinabove, operatively mounted to a crane and adapted to monitor a plurality of operating conditions of the crane. A crane monitoring control unit is securely mounted to the crane. A non-volatile memory unit is operatively disposed within the control unit and communicates with the digital processing circuitry. The digital processing circuitry is adapted to execute a set of crane monitoring instructions. The instructions include continuously sampling the data, writing the sampled data set into the non-volatile memory, comparing the crane condition signals to a set of predetermined safe operating parameters, detecting the occurrence and subsequent cessation of an alarm event, generating a discrete event log, and writing the event log into the non-volatile memory.
According to a still further aspect of the present invention, a crane equipped with a crane data acquisition system is provided. The crane comprises a crane support section including a plurality of operative crane components mounted thereto. The crane components include a hydraulically actuated turret assembly rotatable about a vertical axis, and a boom assembly pivotably mounted to the turret assembly and rotatable about a horizontal axis. The boom assembly includes a boom tip disposed at a distal end of the boom assembly. The crane components also include a hydraulically actuated main lift cylinder pivotably interconnected between the crane support section and the boom assembly, a winch assembly, and a cable windable about a drum within winch assembly. The cable extends along the length of the boom assembly and downwardly toward the ground below the boom tip. The crane also includes a crane operator section adapted for use by a crane operator.
A plurality of sensors are operatively mounted to a crane and adapted to monitor a plurality of operating conditions of the crane. Each sensor is operative to generate an electrical crane condition signal representative of one of the monitored crane operating conditions, and to send the crane condition signal over a communication line. The sensors include a tip switch mounted proximate to the boom tip and suspended therefrom in parallel relation to the cable. The tip switch is adapted to detect whether the cable is operating at an excessive angle of inclination. In addition, a pair of main lift cylinder pressure transducers are operatively mounted to the main lift cylinder and adapted to measure hydraulic pressure variations experienced by the main lift cylinder. A pair of turret drive pressure transducers are operatively mounted to the turret assembly and adapted to measure hydraulic pressure developed by the turret assembly during respective left and right rotations of the turret assembly. An accelerometer is operatively mounted to the boom assembly and adapted to measure accelerations and decelerations experienced by the boom assembly.
The crane further comprises a crane monitoring control unit securably mounted to the crane operator section, and which communicates with the plurality of sensors. The crane monitoring control unit includes digital processing circuitry for sampling and processing the crane condition signals, identifying the occurrence of an unsafe crane condition based on a comparison of the crane condition signals against predetermined safe operating parameters, and generating and storing an event log indicative of crane operations causing the unsafe crane condition. The event log includes all crane condition signals sampled over a period of time starting at a predetermined number of seconds preceding the occurrence of the unsafe crane condition and ending at a predetermined number of seconds after a conclusion of the unsafe crane condition.
Accordingly, it is an object of the present invention to provide a system and method for monitoring the conditions under which a crane is operating.
It is a further object of the present invention to provide a system and method for detecting an alarm event during which crane operating conditions have exceeded specified limits.
It is another object of the present invention to provide a system and method for creating an event log containing sensor data and other information describing the circumstances surrounding a crane operating conditions alarm event, and storing the event log for later retrieval and analysis by a device or devices external to the system.
Some of the objects of the invention having been stated hereinabove, other objects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow.